Patient transfer

Prior to achieving any surgical position, the patient must be transferred onto the operating room table. The final position of the patient is of the utmost importance, but achieving these positions requires careful planning and coordination by the operating room team. The overall plan for each patient transfer should be discussed prior to any movement.

Frequently, the patient can assist in positioning prior to induction of anesthesia. However, under general anesthesia, the operating room team must carefully move and position each patient. Pertinent patient comorbidities should be reviewed. For example, patients with morbid obesity or unstable spine fractures will require additional staff for transfer and positioning. When the patient is moved after the induction of general anesthesia, the anesthesiologist must be aware of any blood pressure alterations and ensure a safe systemic blood pressure prior to any patient movement.

All monitors, intravenous lines, and the endotracheal tube need to be carefully managed when moving a patient. The eyes should be taped to avoid corneal abrasion. With excellent communication, patients can be safely and successfully transferred within the operating room.

Beach chair and sitting position

The sitting and beach chair position (BCP) are variations of nearly the same position with similar physiologic changes and potential complications. For this reason, they will be discussed in combination in the following section. For either position, general anesthesia is typically induced in the standard supine position and after successful intubation of the trachea and placement of all further lines and monitors, the patient is transitioned to this more upright position.

Not all cases in this position mandate general anesthesia and patients undergoing procedures using regional anesthesia and light sedation can help assist positioning themselves prior to surgical incision. For the BCP, specially manufactured operating room tables are available to aid in successful placement of the patient in this position. During neurosurgery in the sitting position the head is held in a Mayfield headrest and pins. The final position should have the patient's hips and knees flexed to avoid any stretch on the sciatic nerve. The legs should be kept as high as possible to increase venous return.

What common procedures are performed in this position?

The BCP or sitting positions are used for shoulder arthroscopy and neurosurgical procedures, including posterior cranial fossa and posterior cervical spine.

The benefits of the BCP in orthopedic surgery include access to the anterior and posterior shoulder, reduced traction induced brachial plexus neuropathies, decreased port placement related injuries, decrease operative time, and more anatomic position and movement of the shoulder.

The benefits of the sitting position in neurosurgery include access to the posterior cervical spine and cranial fossa; it also allows for improved venous and cerebrospinal fluid drainage, potentially lowering intracranial pressure. Additionally, the sitting position provides better access to the airway and less facial edema compared to the prone position. However, the sitting position is also associated with several serious risks. For this reason, the overall use of the sitting position for neurosurgical procedures has declined.

What are the common variations of this position?

There are limited variations on the BCP and sitting position. These include varying degrees of head up positioning ranging from true sitting to a more relaxed, semi-recumbent position.

What are the physiologic changes when placing a patient in this position?

In awake patients, transitioning from the supine to upright position causes an increase in systemic vascular resistance (SVR) and systemic blood pressure. This is accompanied by a decrease in cardiac output. However, under general anesthesia the normal hemodynamic responses are altered, limiting the normal increase in SVR. This leads to a decrease in mean arterial pressure and further decrease in cardiac output. For this reason, the patient should be incrementally placed into the sitting position and the blood pressure should be supported with intravenous fluids and vasopressors.

Also, one must be aware of the potential difference in the noninvasive blood pressure recorded at the arm or leg versus actual pressure seen at the brain. Although there is a controversy as to the exact difference, if any, between noninvasive recording and actual brain perfusion, some theories support correcting blood pressure in the sitting position to account for a gravitational effect on the column of blood between the site of measurement and the brain.

Also, one must also be aware of the concept of cerebral autoregulation. A full discussion of cerebral autoregulation is beyond the scope of this chapter.

When managing blood pressure in any upright position, the anesthesiologist must be aware of the potential for the brain to be underperfused if the lower limit of autoregulation is not met intraoperatively. Although the lower limit of autoregulation continues to be debated, strict awareness of intraoperative blood pressure is paramount to providing safe anesthesia to any patient in the BCP or sitting position.

What are the options for anesthetic management?

Neurosurgical procedures in the sitting position typically demand general endotracheal anesthesia with invasive blood pressure monitoring. For shoulder arthroscopy, general anesthesia, regional anesthesia, or the combination of both can be provided.

What complications are associated with this position?

The BCP or sitting position is associated with several potential complications. Intraoperative hypotension is not uncommon during procedures in the sitting position, with an incidence of 12% to 32% reported in the literature. Blood pressure management of patients in the sitting or BCP will not be discussed in detail here, although understanding the role of hypotension in this position and its influence on devastating neurological injury is worth noting.

Rare, major neurovascular injuries following procedures in the BCP have been reported, especially following shoulder arthroscopy. The reported incidence of cerebral injury is estimated at 1 in 22,000 procedures in the BCP or sitting position. These events possibly occurred secondary to improper blood pressure management. Blood pressure must be carefully monitored and hypotension should be treated aggressively. Recent reports discuss the role of monitoring cerebral oxygen saturation in an effort to detect and limit potential neurologic injury. However, further studies are needed to support the routine use of this technology.

Venous air embolism (VAE) can occur in any surgical position and has been documented during Cesarean section, pelvic, laparoscopic, orthopedic, and neurosurgical procedures. VAE can occur whenever a venous pressure gradient exists between an open vein at the operative site and the heart. This is especially present during craniotomy in the sitting position due to the non-collapsing nature of the venous sinuses. During craniotomy, VAE can be seen in nearly all positions including supine and prone.

The incidence of VAE in the sitting position ranges from 6% to 30%. Severe VAE, defined by systemic hypotension, occurred in 1% to 6% of cases. Transesophageal echocardiography (TEE) or precordial Doppler is often used for early detection of VAE.

Major complications from VAE include hypoxia, hypotension, arrhythmia, pulmonary hypertension, and circulatory collapse. Paradoxical air embolism (PAE) can occur through a patent foramen ovale (PFO) leading to major neurological injury or myocardial infarction. For this reason, a PFO is an absolute contraindication to the sitting position.

Other potential injuries occur from malpositioning the patient in the BCP or sitting position. Excessive head flexion can cause arterial and venous obstruction leading to upper airway edema and potential airway compromise following extubation. Additionally, spinal cord injury has been reported after extreme head flexion. Endotracheal tube obstruction can lead to poor and difficult ventilation. The endotracheal tube can also compress the tongue if the head is not positioned correctly, leading to macroglossia and post extubation airway obstruction.

The TEE probe used to monitor for VAE can lead to similar compression of the tongue and larynx, leading to edema and upper airway obstruction. Careful attention and continued monitoring of head position must be performed throughout the surgical procedure.

What strategies can be used to decrease the risk of injury in this position?

During procedures in the BCP or sitting position, the head should be secured in a neutral position to avoid flexion or extension. As a general rule, a minimum of 2-finger breadths distance between the sternum and mandible is recommended when flexion of the head is required in the sitting position. Additionally, careful attention must be paid to all known pressure points. As previously discussed, extra padding should be placed where necessary. The arms must be supported to decrease stretch on the brachial plexus.

Although rare, devastating neurological injury related to hypotension can occur when in the BCP or sitting position. Careful monitoring of the patient’s blood pressure from induction through the completion of the procedure can be performed with either noninvasive or invasive monitors. Aggressive treatment of any periods of hypotension should be performed. If using a noninvasive blood pressure cuff, the site of measurement should be on the arm rather than the leg.

However, with either site, the anesthesiologist must recognize the potential for lower perfusion pressure at the brain in the sitting position as compared to the arm or leg. If invasive blood pressure monitoring is employed, zeroing the transducer at the level of the tragus or circle of Willis should be contemplated.

To avoid major complications related to VAE, precordial Doppler or TEE can be used for early detection. If VAE is detected, notification of the surgical team and swift treatment can potentially decrease the risk of debilitating stroke or coronary ischemia.